Process of coating cartridges



Patented Nov. 4, 1930 PATENT OFFICE JOHN DOUGLAS PEDERSEN, OF SPRINGFIELD, MASSACHUSETTS rnocnss or ooarmoflomrmnens 11,0 Drawing.

This invention relates to a process for coating cartridges and more particularly the affixing of a coating of hard wax to the metal case of a cartridge; and the object of the invention is to provide a method whereby cartridges may be coated with great uniformity with an extremely thin film, and also whereby a relatively large number of cartridges may be coated in a short time and at small cost.

In the preparation of cartridges having metal cases for storage and for use, it has been found desirable to apply to said metal case a relatively thin coating of some protective substance which will preserve said metal case for comparatively long periods of time against-deterioration, such as season cracking. In the present invention, the material for said coating has been so chosen as to perform the additional function of acting as a lubricant for the case of the cartridge, both for facilitating introduction into the chamber of the gun and the extraction thereof after firing. The most suitable wax which I have found for this purpose and which I at present prefer is ceresin, a refined product of ozokerite; but I wish it to be understood that other waxes having similar qualities may exist which might serve equally well. Some of the desirable features of ceresin are that it is hard and non-tacky at ordinary temperatures having a melting point somewhere between 140 and 176 Fahrenheit. It is smooth and glassy when hard and does not gather dirt or dust. However, when the ceresin on the cartridges is melted in the chamber of a gun, it becomes a lubricant.

Other lubricating waxes have been employed for coating cartridges, and the method most generally pursued for applying said coating to the cartridge case has been to prepare a heated bath of a solution of the wax in a suitable solvent, dip the cartridges therein so that a film of the solution will adhere thereto, and finally withdraw the cartridges to permit the solvent to evaporate from the coating film. This former process is comparatively slow and has been found lacking in several important respects.

It is of great importance that the protective film 0n the cartridge be of uniform thick- Application filed January 27, 1928. Serial No. 250,090.

ness so as not to vary appreciably the ganging fit of the cartridge when working through the automatic loading and extracting mechanism of. a gun. It is also desirable for commercial reasons that the process of coating be accomplished as rapidly as possible.

.Under the former method, when a large batch of cartridges at ordinary room temperature is simultaneously dipped into a heated bath of the dissolved coating material, the bath is lowered in temperature by the introduction of the charge and the thickness of coating adhering to the cartridge casings will vary since it depends largely on the viscosity of the solution, which in turn is dependent upon the temperature of the bath. Due to the difiiculty under such methods of maintaining the solution at uniform temperature, the thickness of the film on different cartridges is likewise non-uniform. Furthermore, the evaporation of the solvent from the coating after the cartridges are withdrawn from the bath is comparatively slow, and this is particularly true in the case of a ceresin wax coating. Attempts to hasten the evaporation in hot rooms or by heated air exteriorly applied to the cartridges have not met with the success to be expected from the amount of heat thus employed. Possibly the reason is that the coating film when dried by an outside heat forms first a thin insulating skin which impedes the penetration of the drying heat. In any event, such drying is slow and the production in quantity of cart-ridges coated in this manner becomes unduly expensive.

To avoid these difiicultics. I have proposed a method for afiixing the film coating to the cartridge case which involves first the preheating of the cartridge cases, said preheating being to approximately the same tem--. perature as that of the heated bath. Then when a charge of cartridges is introduced into the bath, no change in temperature of the latter will take place; and furthermore, when the charge of cartridges is withdrawn from the bath, the still heated condition of the cases will greatly accelerate the drying or evaporation of the solvent in the coating film, thus speeding up the process. It has been found that the interior heat of the car tridge case is much .more efiective in drying out the coating film than heat exteriorly applied thereto.

More specifically, my process consistsin pre aring a solution of coatin material, pre erably ceresin wax dissolv in carbon tetrachloride, and in heating said solution to an approximate temperature of 100 to 120 Fahrenheit. The amount of ceresin in the solution will be approximately 7% of the entire liquid bath. The cartridges to be coated are also heated toapproximately this same temperature. so that there will e no heat exchange when the cartridges and the coating solution are brought into contact.

The method of applying the coating solution to the cartridge cases may be accomplished by dipping, spraying or brushing, and in the practical carryingout of my process I have employed dipping the cartridge cases into a heated liquid bath of the coating solution. The time of immersion may be relatively short. Upon withdrawing the cartridges from the bath, the coating thereon may be dried by evaporation in the air at the ordinary temperature of the room," or it may be accelerated by being subjected to a current of heated air. As beforestated, the heated condition of the cartridge case will greatly accelerate the drying out or evaporation of the solvent from the coating film.

The preheating of the cartrides. before introduction into the bath may 'e accomplished in various ways, either by an oven or by being dipped into aheated liquid of the temperature desired, which liquid may conveniently be the same as the solvent for the wax of the coating. By thus preheating, the cartridge cases preparatory to their immersion into the heated coating bath, the latter can be conveniently kept in a bath of relatively small proportions because of the absence of any change in temperature thereof when the charge of cartridge cases is introduced therein. Due. also to the fact that the immersion of the cartridges into the bath need be but momentary, it becomes quite practical to arrange apparatus for a continuous travel of the cartridges in and out of a preheating chamber or liquid bath, in and out of the coating bath, and in and out of the final drying chamber. An employment of the process in such a manner will greatly speed up the coating of cartridges over the methods heretofore employed, while at the same time producing a product of great uniformity as to the thickness of the coating film. Obviously the coating may be thickened by a repeated dipping and drying of successive coats, and thus the process may be adjusted to give any thickness of coating desired.

While I appreciate that various changes and modifications of the steps as above outlined may be made, I wish it to be understood that such changes will still' be within the purview of the invention if fairly embraced y the language of the claims which follow.

What I claim is:

1. The process of aifixing a coatin' film of hard wax such as'ceresin to the sur ace of a metal cartridge case which consists in first heating said case to a temperature which will accelerate the vaporization of the solvent to be later applied, then applying to the surface,

of said preheated case a hot solution of the hard wax to form a thin film thereon, and finally allowing said solvent thereof to vaporize in the air under the accelerating etlect to form a thin film thereon, said solution also being at a temperature of approximately 100 to 120 F., and finally allowing said solvent thereof to vaporize in the air under the acceleratin g effect of the preheated case to produce a hard dry coating 'film of wax on said case.

3. The process of aflixing a coatin film of hard wax such as ceresin to the surface of a metal cartridge case which consists in a substantially continuous travel of said case first through a heating chamber to preheat the same, then through a bath of a hot solution of said wax at approximately the same temperature as said preheated case, whereby said case receives a coating film thereon, and finally through a drying chamber of air to vaporize the solvent from said film under the accelerating effect of the preheated case to produce a hard dry coating film of wax on said case.

4. The process of aflixing a coating film of hard wax such as ceresin to the surface of a metal cartridge case which consists in a substantially continuous travel of said case first through a heating bath of solvent of said Wax to preheat said case, then through a bath of a hot solution of said wax in said same solvent at approximately the same temperature as said heating bath, whereby said case receives a coating film thereon, and finally through a drying chamber of air to vaporize the solvent from said film under the accelerating effect of the preheated case to produce a hard dry coating film of wax on said case.

In testimony whereof I have aflixed my signature.

JOHN DOUGLAS PEDERSEN. 

